As a high-performance permanent magnet, there have been known rare-earth magnets such as a Sm—Co based magnet and a Nd—Fe—B-based magnet. When a permanent magnet is used for a motor of a hybrid electric vehicle (HEV) or an electric vehicle (EV), the permanent magnet is required to have heat resistance. In a motor for HEV or EV, a permanent magnet whose heat resistance is enhanced by substituting a part of Nd (neodymium) in the Nd—Fe—B based magnet with Dy (dysprosium) is used. Since Dy is one of rare elements, there is a demand for a permanent magnet not using Dy. The Sm—Co based magnet has high Curie temperature, and it is known that the Sm—Co based magnet exhibits excellent heat resistance with a composition system not using Dy. The Sm—Co based magnet is expected to realize a good operating characteristic at high temperatures.
The Sm—Co based magnet is lower in magnetization compared with the Nd—Fe—B based magnet, and cannot realize a sufficient value of the maximum energy product ((BH)max). In order to increase the magnetization of the Sm—Co based magnet, it is effective to substitute a part of Co with Fe, and to increase an Fe concentration. However, in a composition range having a high Fe concentration, a coercive force of the Sm—Co based magnet tends to reduce. Further, the Sm—Co based magnet is made of a fragile intermetallic compound, and is generally used as a sintered magnet. Therefore, brittleness of the Sm—Co based magnet is liable to be a problem in view of fatigue characteristics. In the Sm—Co based sintered magnet having a composition with a high Fe concentration, enhancement in mechanical properties such as strength and toughness in addition to improvement in a magnetic property such as a coercive force is required.